Chronic pain is pain that persists beyond the expected healing time, if resulting from injury, and can progress from a bothersome nuisance to a profound affliction. Chronic pain can cause a marked alteration in behavior with depression and anxiety, restriction in daily activities and excessive use of medication and medical services in an afflicted individual. The treatment of chronic pain is difficult, often inadequate and associated with high economic and psychological cost.
Buprenorphine is a partial μ-opiate receptor agonist, an ORL1/nociceptin receptor agonist with high affinity and a slow dissociation rate and a κ-opiate receptor antagonist.
Buprenorphine is metabolized by the liver, via the CYP3A4 isozyme of the cytochrome P450 enzyme system, into norbuprenorphine (by N-dealkylation) and other metabolites. Buprenorphine has a low oral bioavailability due to very high first-pass metabolism.
Buprenorphine is an analgesic, available commercially as Temgesic® 0.2 mg sublingual tablets, and as Buprenex® in a 0.3 mg/ml parenteral formulation. Buprenorphine is also available as a sublingual preparation (Subutex®) and as a sublingual abuse-resistant formulation with naloxone (Suboxone®). The FDA approved Suboxone/Subutex in 2002 as a treatment of opioid dependence. Sublingual buprenorphine has been used for opioid detoxification and maintenance.
A recent open-label study used sublingual buprenorphine (Suboxone®) for the treatment of chronic pain to those chronic opioid users (Malinoff et al., 2005, American Journal of Therapeutics 12, 379-384). Patients were treated with daily buprenorphine doses that ranged from 2-20 mg (mean 8 mg). The treatment lasted from 2.4 months to 16.6 months (mean 8.8 months). The article reports that patients experienced improvement in their condition and reported a decrease in their sensation of pain.
Still, effective methods for treating chronic pain that are not associated with adverse effects are needed, especially to those opioid naive or opioid experienced patients.